Hermetically sealed proximity fuze



Nov. 14, 1961 FIG.!

N. D. FOLEY 3,008,415

HERMETICALLY SEALED PROXIMITY FUZE Filed Nov. 17, 1949 F I G. 2

INVENTOR.

NELSON D. FOLEY ATTORNEY 3,%8,4l Patented Nov. 14, 1961 3,008,415 HERMETICALLY SEALED PROXIMHTY FUZE Nelson D. Foley, Silver Spring, Md, assignor to the United States of America as represented by the Secretary of the Navy Filed Nov. 17, 1949, Ser. No. 127,835 6 Claims. (Cl. 102-702) The present invention relates to improved hermetically sealed proximity fuze structure.

In radio proximity fuzes as designed and constucted up to the present time much difiiculty has been experienced with failure of fuzes to operate due to the entry of moisture into the interior of the fuze casing. More particularly, it has been found that moisture causes damage, with the result that the life of the fuzes is greatly reduced when they are subjected to the effects of high temperatures, extreme humidity and other conditions found in service. Experience with radio proximity fuzes has proven definitely that waterproofing, to be effective, must be inherent in the fuze and not dependent upon compression or gasket seals, or seals of any composition subject to short-time deterioration.

In addition to their inability to withstand conditions of high humidity, as above stated, the present radio proxirnity fuzes have been found to be incapable of successful firing at relatively high velocities, because of the softening and collapsing of the plastic noses under the high temperature engendered. Further, collapse of the front case or nose due to pitting under high temperature may cause premature operation of the fuze if the projectile receives a high potential charge when leaving the ionized cloud of' the gun blast. Such premature operation is attributed to the dissipation of the charge caused by the spinning off of melted particles on the front case.

Therefore, one of the principal objects of the present invention is to provide radio proximity fuze structure wherein all the critical components are enclosed within a hermetically sealed'can, to the end that effective waterproofing will be assured.

Another object of the invention resides in the provision of fuze structure embodying improved high-temperature-resisting material for the nose or front case to the end that failures and prematures due to collapse of noses of plastic material will be avoided and premature operation due to such nose failure prevented.

The invention seeks, as a further object, to provide a radio proximity fuze having longer shelf life, greater mechanical stability and improved performance at high velocities and high temperatures and under extremely high set-back forces.

Still another object of the invention is to provide proximity fuze structure wherein the critical components are contained within a hermetically sealed can and within an amplifier shield-can to constitute a standard capsule which may be built in quantity and stored, any one of a variety of oscillator assemblies being attachable to said capsule at any time.

Other objects and many of the attendant advantages of this invention will be appreciated readily as the same becomes understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a longitudinal sectional view, partly in elevation, of fuze structure according to the invention;

FIG. 2 is a longitudinal sectional view of the waterproofing casing, certain of the contents being shown; and

FIG. 3 is an end view of the shield can.

Referring now to the drawings in detail and first to FIG. 1 thereof, the numeral 1 indicates generally the improved fuze. The fuze, according to this invention,

includes an outer casing 2 which is provided with an internally threaded rear end portion 3 into which is screwed a safety unit 4 of the twin rotor type described in patent application Serial No. 534,785, filed May 9, 1944 for Safety Device, now Patent No. 2,711,695. The safety unit 4 is provided with an extended counterbored internally threaded portion 5, which receives a conventional auxiliary detonator 6.

Inwardly of the unit 4 is a partition 7 having a central aperture 3 located to aline with appropriate apertures in the unit 4 and with a discharge opening in the squib unit, described in detail hereinafter.

As pointed out in the objects set forth, an important purpose of the invention is to provide scaling for those components of a radio proximity fuze which are most susceptible to damage due to Weather changes. To this end there is provided a can 9 of relatively thin sheet metal and of such diameter that it will fit snugly within the casing 2. The can 9 is seen best in FIG. 2 of the drawings and, by referring to this view, it will be observed that said can, which is of drawn steel, is formed with a cylindrical side wall 10. The can is closed at its rear end by an end wall 12. 'It will be noted that the rear end 12 of the can 9 has a spot of reduced thickness of metal at its center, as shown at 33. This thin spot affords an easy centrally located path for the flash from the squib to the detonator.

Enclosed within the can 9 are a deferred action battery 13 and a delay-self-des-truction unit 14 which contains a squib 15, seen fragmentarily in FIG. 1, positioned so that when the fuze operates the resulting blast will puncture the rear end wall 12 and enter the auxiliary detonator through the aperture 8 and the apertures in the unit 4.

The invention contemplates the provision of a standard proximity fuze amplifier, which is shown generally at 16. A shield can 17 of metallic material surrounds the amplifier and is secured to the base 18 thereof. The base 18 is provided with a radial flange 19 which overlies a flange 11, formed on can 17, and is secured thereto by spot welding, in at least three places. As will be seen, the amplifier is connected electrically with the battery 13 by pins 20 which engage in sockets carried in the battery turrets 21.

v Referring to FIG. 3, there are shown three terminals 39 each of which is insulated from the shield can 17 by a bead 40 of a suitable glass such as used in Kovar seals and which will make a gas-tight fused seal with the steel of the can 17. Originally each terminal 39 is a Kovar tube of very small bore. The terminal wires from certain of the electrical components within the can 9 and the shield can 17 are passed through these tubes. Said Wires are then cut off at proper length, and soldered to the Kovar tubes, to constitute said external terminals 39.

Another opening 41 is made somewhat larger than the wire 42 which passes through it. This wire is the ground and eventually is soldered to the metal surrounding it, thus at the same time closing the opening 41 hermetically with the solder. However, before this is done, the potting compound is introduced through the opening 43, while the end shown in FIG. 3 is uppermost. During this time, the air will escape through opening 41.

When the potting is completed, opening 41 is closed by soldering, and then the tightness of the entire device is tested by applying compressed air to opening 43. If there are no leaks, this opening is then closed by a disc or pin, which is soldered in place to complete the sealing of the capsule.

It should be understood that, in assembling, the safety delay-self-destruction unit 14 is first placed in the can 9, and the battery 13 is then placed in said can and the amplifier unit 16 secured in place and properly connected with the bat-tery. A rubber disc 38 is located between '"the'unit l l'andthebattery13; as shown. The'who'le operation is efiectedin such manner that the entire unit will be hermetically sealed and thus will form a standard unit or capsule to be used'with oscillators of various types, in

a manner discussed in detail hereinafter.

' Inasmuch as the individual units to be accommodated then subjected to suitable compression. 'While' thus compressed, the open end of thelca'sin-g is"sheared oh. to make its internal length correct. 'This will leave it in proper condition to slip over'the'rear'end of the base 18.

While so positioned, the can 9 is spot-welded to the said base'1 8 at at Ie'ast'f'our' places, so as to hold it firmly,

with compression on' the'enclosedhnits. The spots are next cleaned to" accept solder; the flange 31 is turned over flat against the rear face of the flange 19', and a continuous solder fillet 32 is for-medaround the jointtoseal" the shield can 17 hermetically to the can 9 attheir junction. An oscillator unit for the invention is shown in FIG. 1.

I This unit comprisesa skeleton base member 22 of molded plastic material with an attaching skirt 23 of metallic materialand of generally frusto-conical shape molded thereinto. A coil form 24 of (generally cylindrical shape, and

provided with a spiral groove to receive the coil turns, is

'fitted in a cylindrical grooveaxially of the base 22; As

shown in dotted lines, the base '22 is formed with an annularly arranged cluster of recesses 25 to receive the resistors, chokes and capacitors employed in the oscillator I circuit. One of said chokes is shown at 26. The'oscillator vacuum tube 27 is carried in an axial recess 28 in I the base 2.2,said recess being constricted near its rear end to limit thetube against rearward displacement. The

leads of the tube are connected with the other components by suitable conductors in a Well known manner.

The oscillator unit is of the general type disclosed in filed March 4, 1946, for Fuze. More particularly, the

I antenna comprises a curvilinearly arranged strand of wire 29 which is turned over a generally conical plastic nose 30 and embedded in the surface thereof. The antenna 29 may be an extension of the oscillator tank coil, 'whichis an impedance matching transformer wound-about 'the form 24. All of -the components are retained rigidly in position 'on the base. by injection of a plastic material having'suitable' heat-resisting characteristics and are of sufficient ru'ggednessto withstand the forces acting on the radio proximity fuze whilebeing fired from a gun.

The nose of the fuze'hasa plastic end piece 34. This is'subjected to a' heatingefiect when the fuze moves through the atmosphere at high velocity. Materials here, tofore used were objectionable in that the heat thus produced softened the plastic, and'the tremendous air friction abraded particles from the softened surface. When a projectile is fired from a'l'gun, it must traverse the cloud of ionized smoke orother particles at the mouth of the gun barrel. In doing so the surface of the fuze nose becomes charged. At this time the fuze is not yet armed, hence'no'firing occurs due to thecharge. However, the fuze is in the armed condition when the above mentioned heating and soften-ing occur, hence the re moval of particles from its surface by air friction may dissipate the charge, thus causingan-elec'trical disturbance I vvhich may be sufficient to actuate the fuze prematurely."

mana e piece 34 according to the presentinvention is 4 9 have tolerances of over-all lengths, there may be a considerable variations in the'tot als' when assembled. To make it "possib'le'to seal the in -the'can' under the "requisite pressure, they ar'e'first inserted in the can, and

not subject'to this action because it consists of aplastic, which, for the purposes here involved, is indestruotlble.

The material is chemically identified as polytetrafluoroethylene, a plastic developed by du Pont. I This substance does not melt, and is not attacked by any acid or gas. Ex'tre'me" heat doesnot soften'or' char 'itjbut merely causes a slight superficial volatilization; -Its'e"l'ectrical and 111011- hygroscopic properties are superiortothose of polystyrene, and its mechanical resistance to flexure and impact are comparable to those of ethocel. I

The nosepiece 34'is machined to provide an inte a1 thread 3'5 fittingoirthe corresponding thread ofthe metal base member '36. ,The'fia'nge37 is then 'pre's'sedflown against the nose piece 34 to complete the nose. 'Alternatively, the plastic may be m olded directly to an insert,v -with equivalent anchoring means or methods,

' Obviously many modification's and: variations ofjthe present invention are possible in the lig htaof the above teachings. It is therefore to be understood that withm the scope of the appended claims the invention may be practiced otherwise than as 'specifically described; What is'claimed is: V 1. In a proximity -fuze; an assembly comprising an amplifier, a deferred action source'of po'wer; a squib and a safety device, and a hermeticallysealedmetallic container enclosing the said assembly, said container having a top'wall formed with openings, terminals projectfrom the'wall. I I I 2. A nose for a fuze having a casing-made of poly patent application of J. J. Hopkins, Serial No. 651,871, l

mg therethrough, and'means insulating the terminals tetrafiuoroethylene.

I 3. The process of making a proximity ,fuz ei" assembly containing electrical and mechanical components, hermetically sealed in a container, which consists in inserting the components in the containensubjecting them to' pressure to 'force theminto'intimate end-to-end contact length to accommodate them in their compressed condition, and thereupon sealing the containerihermetically' While I maintaining this condition. I

4. A hermetically sealed assembly tor use asa'unit' of a proximity'fuze; comprisingtwo metal cupseach havand a squib, said thrice last" named devicesbeing housed mouth 'andhenneticallysealed toeach other. I

I 5. 'An assemblyas defined 'iniclaim 4, ha ving in addition an an'riular'fiange projecting outwardlyfroni the assembly at the line of junction of the cups with each other;

' 110, March and April 1947."

Electronics for 'November 1948,' pages -82;

Y in said-cups jointly, said cups being' loc'ated mouthto with one anothe r cutti ng' the container to' the correct 'ing a closed end, electronic apparatus,1a power" source,

Radio Proximity Fuse Design, National Bureau of Standards Research Paper 31 1723, July 1946.; (Sup. Doc., U.S. G.P.O., Washington '5, DC.) 7

Survey of Proximity Fuse DeveloprnlentjPageet .21.,

American Journal of -Phy 'sics, 'vol.= 15, No. '2, pages Hermetically Sealed Electronic Components,'Leiss mi -e I 

